Active and multifunctional packaging materials are facing increasing demand because of the changing trend of the customer needs such as safety and long shelf life of the food material without however interfering with processed materials, preservatives and additives. Contrary to conventional food packaging that is inert to the food; active food packaging has the ability to act against the contaminants and to remove them. Active packaging functions like being antibacterial, ability to scavenge spoiling molecules, and impermeability to gases are achieved by the integration of active components into the food packaging materials. In order to have safe active food packaging, it is crucial to choose active packaging components that do not pose any risks to human health.
In prior art, antibacterial properties are imparted to the food packaging material through incorporation of antibacterial agents including organic acids, bacteriocins, and silver ions. These agents were proven to result in packaging material that can act against food pathogens (WENG Y.-M., Chen M.-J., Chen W., Antimicrobial Food Packaging Materials from Poly(ethylene-co-methacrylic acid), LWT—Food Science and Technology, 32, 191-195, (1999); MAURIELLO G., Ercolini D., La Storia A., Casaburi A., Villani F., Development of polythene films for food packaging activated with an antilisterial bacteriocin from Lactobacillus curvatus 32Y, Journal of Applied Microbiology, 97, 314-322, (2004); SCAFFARO R., Botta L., Marineo S., Puglia A. M., Incorporation of Nisin in Poly (Ethylene-Co-Vinyl Acetate) Films by Melt Processing: A Study on the Antimicrobial Properties, Journal of Food Protection&#174; 74, 1137-1143, (2011); LEE J., Lee Y.-H., Jones K., Sharek E., Pascall M. A., Antimicrobial packaging of raw beef, pork and turkey using silver-zeolite incorporated into the material, International Journal of Food Science & Technology, 46, 2382-2386, (2011); MARTÍNEZ-ABAD A., Ocio M. J., Lagar& J. M., Sanchez G., Evaluation of silver-infused polylactide films for inactivation of Salmonella and feline calicivirus in vitro and on fresh-cut vegetables, International Journal of Food Microbiology, 162, 89-94, (2013)).
There are provided safer and more natural alternatives of antimicrobial agents, namely essential oils which are volatile components of herbs and spices, and many of them and their active components have been proven to have antibacterial activity against food pathogens. Among these, thyme oil and cinnamon oil are particularly preferred as they have the well established antimicrobial activities against different bacteria because they include carvacrol and cinnamaldehyde, respectively, as the major components (FRIEDMAN M., Henika P. R., Mandrell R. E., Bactericidal Activities of Plant Essential Oils and Some of Their Isolated Constituents against Campylobacter jejuni, Escherichia coli, Listeria monocytogenes, and Salmonella enterica, Journal of Food Protection, 65, 1545-1560, (2002); ARORA D. S., Kaur J., Antimicrobial activity of spices, International Journal of Antimicrobial Agents, 12, 257-262, (1999)). Further, Paula et al. reports that carvacrol from thyme oil and cymene from cinnamon oil synergistically improve controlling of the growth and viability of Listeria monocytogenes cells (PAULA M. P., Bego, Ntilde, A D., Pablo S. F., Aacute, Ndez, Alfredo P., Use of Carvacrol and Cymene To Control Growth and Viability of Listeria monocytogenes Cells and Predictions of Survivors Using Frequency Distribution Functions, Journal of Food Protection, 67, 1408-1416, (2004)). In another assay, Yossa et al. reports that cinnamaldehyde of the cinnamon oil eliminates completely the E. coli and Salmonella cells (YOSSA N., Patel J., Macarisin D., Millner P., Murphy C., Bauchan G., Lo Y. M., Antibacterial Activity of Cinnamaldehyde and Sporan against Escherichia coli O157:H7 and Salmonella, Journal of Food Processing and Preservation, nia-n/a, (2012)). Essential oils have been incorporated into the polymeric films as a way of developing safe antibacterial food packaging material. While this approach results in some antibacterial activity, the effectiveness is very low compared to the activity of free essential oils. A system that enables controlled loading/release of essential oils into/from the polymeric films that enhances the antibacterial activity of the food packaging material is needed.
There are various methods and products in the art, for preserving food material from negative effects of ethylene gas. Fruits and vegetables, for instance secrete ethylene as a phytohormone, and this accelerates the ripening and consequently rotting and deterioration of the food material which is undesirable. A method to introduce ethylene scavenging properties for instance involves using of potassium permanganate as an ethylene oxidizing agent as disclosed in WO 2005/000369 A1 and EP 0 515 764 A2. Potassium permanganate is incorporated into absorbent materials having high surface area such as alumina, silica, clay and activated carbon. However potassium permanganate is prohibited in Europe and limited latitude exists in the U.S. as far as the absorbent material is stored in sacs because of the toxicity of potassium permanganate. Incorporating different minerals into polymeric films, on the other hand is also well known and such products are already available in the market (e.g. Peakfresh®, Australia; Greenbags, U.S.A.; Magiclivefresh, Turkey).
Food packaging materials with barrier properties against atmospheric gases, water vapor and volatile compounds are required. Synthetic polyolefins which have excellent thermal and mechanical properties are disadvantegous as food packaging materials due to their permeability to gases. While the use of multilayered polymeric films ensures barrier properties, their high cost and problems associated with recycling these films limit their commercial use. Therefore, in prior art, alternative materials to be incorporated within polyolefins for ensuring the aforesaid properties in packaging materials have been focus of the researchers. Nanoclay particles, mainly montmorillonite have been applied as fillings in nanocomposites as barrier components against gas molecules (DUNCAN T. V., Applications of nanotechnology in food packaging and food safety: Barrier materials, antimicrobials and sensors, Journal of Colloid and Interface Science, 363, 1-24, (2011); GOPAKUMAR T. G., Lee J. A., Kontopoulou M., Parent J. S., Influence of clay exfoliation on the physical properties of montmorillonite/polyethylene composites, Polymer, 43, 5483-5491, (2002); HAMBIR S., Bulakh N., Kodgire P., Kalgaonkar R., Jog J. P., PP/clay nanocomposites: A study of crystallization and dynamic mechanical behavior, Journal of Polymer Science Part B: Polymer Physics, 39, 446-450, (2001)). Barrier properties can be achieved if effective adhesion between the fillings and the polymer occurs, which is however hardly achievable. Montmorillonite exhibits good compatibility with polymers having higher surface energy such as polyamides, albeit is problemmatic with polymers of having lower surface energy such as polyethylene (PE) and polypropylene (PP) because of the lower adhesion of such polymers that causes the nanoclay molecules be hardly dispersible in the polymer blend.
Therefore, there exists continuing need for a modified film packaging that can have antimicrobial, gas scavenging and barrier properties while having also easy applicability to conventional olefins, particularly thermoplastics and more particularly to plastics of having lower surface energy such as PE and PP.
Nanocomposite materials including halloysite nanotubes incorporated into polymeric moieties such as thermoplastic polymers are disclosed, for instance in CN 1746216 A and US 2007106006 A1, whereas the said composite materials are proposed for different application areas such as coatings for fire retarding, anti-corrosion and self-cleaning of surfaces as well as plastics of different functionalities. However, there appears no study within state of the art as to the use of such nanocomposites in the form of plastic films as a food packaging material. The present invention eliminates the problems faced in the prior art by way of using the packaging materials incorporated with halloysite nanotubes which are found as efficient materials to provide good antibacterial, barrier and scavenging properties in the specific area of food products by simple production and modification procedures.
It is therefore an objective of the present invention to provide a food packaging material in the form of polymeric films or a coating for polymeric films having good antibacterial, barrier and scavenging properties.
A further object of the present invention is to provide antibacterial properties without using agents detrimental or harmful to human health.
Another object of the present invention is to provide packaging materials having satisfactory barrier and scavenging properties while being easily recyclable.
Still a further object of the present invention is to provide modified polymeric films for food packaging providing all of antibacterial, barrier and scavenging properties within the same product by specific arrangements and modifications.
Further objects and aspects of the current invention shall be apparent for those skilled in the art in view of the following statements and description, and these objectives are presently solved by novel products and specific uses thereof as disclosed in the appended claims.